Acute lung injury (ALI) and its more severe form, adult respiratory distress (ARD), is a devastating clinical syndrome of sudden lung inflammation that results in severe edema and hypoxemia and requires care in the intensive care unit. Mortality is between 30-40% in controlled settings. To date, no single drug has proven effective for improving mortality in ALI/ARDS despite many large and small clinical trials. The objective of the Clinical Research Network (ARDSNet) is to develop and conduct clinical research trials to prevent, treat, and improve the outcome of patients with acute lung injury, acute respiratory distress syndrome, and possibly other related critical illnesses. Enroll a minimum of 30 patients per year with ALI/ARDS. Describe in detail the gender and racial characteristics of the patient population. Set priorities for and participate in protocol development, developing specific protocols, determination of subject eligibility criteria, developing procedures for electronic transmission of data, developing sample consent forms. Be voting members of the SC;attend meetings and teleconferences. Participate in one or more of a number of subcommittees (e.g., publications, ethics, pathology, natural history, and progress assessment) which will hold meetings and teleconferences on an as-needed basis. Investigators may be asked to participate in Protocol Review Committee (PRC) and Data and Safety Monitoring Board (DSMB) meetings and teleconferences to serve as a resource.